Broadband satellite communication services are becoming more readily available to users onboard mobile platforms such as aircraft, ships, trains, buses, automobiles, etc. Generally, such broadband services require relatively large, heavy and expensive antennas mounted to the mobile platform. These large broadband antennas cannot practically or affordably be carried on smaller, light weight mobile platforms. In addition, many smaller mobile platforms do not require broadband connectivity, but instead an inexpensive, small and reliable communication system would be more suitable. That is, smaller mobile platforms may merely need a communication system that will provide low data rate messaging and/or the capability for the mobile platform to be tracked, e.g. geolocated.
For example, smaller mobile platforms may find it useful to employ a satellite based communication system that provides two-way, narrowband communication for general messaging and safety critical communications using small, light weight, low power and low cost antennas that have high reliability. Such narrowband communication system are typically only implemented at frequencies below 2 GHz and are only utilized to provide such services as text messaging, aeronautical information for flight safety, weather reports, and limited web surfing.
Additionally, regulatory requirements have generally prevented the use of wide beamwidth satellite communication antennas because of interference with adjacent satellites that occurs. For example, when communication with satellites at C-band and Ku-band, FCC and ITU regulations generally require the diameter of the antennas to respectively be at least three meters and one meter. With these size antennas, broadband communication at approximately 2-30 Mbs can be achieved, but the size of the antennas is far too large for many mobile platform.
Therefore, it would be desirable to provide a communication system capable of providing low data rate messaging and/or surveillance, i.e. geolocation and tracking, services onboard smaller mobile platforms. Moreover, it would be desirable to provide a satellite communication system for mobile platforms that offers the benefits of small, inexpensive antennas at operating frequencies that correspond to the principal commercial satellite communication bands above 2 GHz.